/* sbt -- Simple Build Tool
 * Copyright 2010 Mark Harrah
 */
package sbt

import Types._
import scala.reflect.Manifest

// T must be invariant to work properly.
//  Because it is sealed and the only instances go through AttributeKey.apply,
//  a single AttributeKey instance cannot conform to AttributeKey[T] for different Ts

/** A key in an [[AttributeMap]] that constrains its associated value to be of type `T`.
* The key is uniquely defined by its [[label]] and type `T`, represented at runtime by [[manifest]]. */
sealed trait AttributeKey[T] {

	/** The runtime evidence for `T` */
	def manifest: Manifest[T]

	@deprecated("Should only be used for compatibility during the transition from hyphenated labels to camelCase labels.", "0.13.0")
	def rawLabel: String

	/** The label is the identifier for the key and is camelCase by convention. */
	def label: String

	/** An optional, brief description of the key. */
	def description: Option[String]

	/** In environments that support delegation, looking up this key when it has no associated value will delegate to the values associated with these keys.
	* The delegation proceeds in order the keys are returned here.*/
	def extend: Seq[AttributeKey[_]]

	/** Specifies whether this key is a local, anonymous key (`true`) or not (`false`).
	* This is typically only used for programmatic, intermediate keys that should not be referenced outside of a specific scope. */
	def isLocal: Boolean

	/** Identifies the relative importance of a key among other keys.*/
	def rank: Int
}
private[sbt] abstract class SharedAttributeKey[T] extends AttributeKey[T] {
	override final def toString = label
	override final def hashCode = label.hashCode
	override final def equals(o: Any) = (this eq o.asInstanceOf[AnyRef]) || (o match {
		case a: SharedAttributeKey[t] => a.label == this.label && a.manifest == this.manifest
		case _ => false
	})
	final def isLocal: Boolean = false
}
object AttributeKey
{
	def apply[T](name: String)(implicit mf: Manifest[T]): AttributeKey[T] =
		make(name, None, Nil, Int.MaxValue)

	def apply[T](name: String, rank: Int)(implicit mf: Manifest[T]): AttributeKey[T] =
		make(name, None, Nil, rank)

	def apply[T](name: String, description: String)(implicit mf: Manifest[T]): AttributeKey[T] =
		apply(name, description, Nil)

	def apply[T](name: String, description: String, rank: Int)(implicit mf: Manifest[T]): AttributeKey[T] =
		apply(name, description, Nil, rank)

	def apply[T](name: String, description: String, extend: Seq[AttributeKey[_]])(implicit mf: Manifest[T]): AttributeKey[T] =
		apply(name, description, extend, Int.MaxValue)

	def apply[T](name: String, description: String, extend: Seq[AttributeKey[_]], rank: Int)(implicit mf: Manifest[T]): AttributeKey[T] =
		make(name, Some(description), extend, rank)

	private[this] def make[T](name: String, description0: Option[String], extend0: Seq[AttributeKey[_]], rank0: Int)(implicit mf: Manifest[T]): AttributeKey[T] = new SharedAttributeKey[T] {
		def manifest = mf
		def rawLabel = name
		val label = Util.hyphenToCamel(name)
		def description = description0
		def extend = extend0
		def rank = rank0
	}
	private[sbt] def local[T](implicit mf: Manifest[T]): AttributeKey[T] = new AttributeKey[T] {
		def manifest = mf
		def rawLabel = LocalLabel
		def label = LocalLabel
		def description = None
		def extend = Nil
		override def toString = label
		def isLocal: Boolean = true
		def rank = Int.MaxValue
	}
	private[sbt] final val LocalLabel = "$local"
}

/** An immutable map where a key is the tuple `(String,T)` for a fixed type `T` and can only be associated with values of type `T`.
* It is therefore possible for this map to contain mappings for keys with the same label but different types.
* Excluding this possibility is the responsibility of the client if desired. */
trait AttributeMap
{
	/** Gets the value of type `T` associated with the key `k`. 
	* If a key with the same label but different type is defined, this method will fail. */
	def apply[T](k: AttributeKey[T]): T

	/** Gets the value of type `T` associated with the key `k` or `None` if no value is associated. 
	* If a key with the same label but a different type is defined, this method will return `None`. */
	def get[T](k: AttributeKey[T]): Option[T]

	/** Returns this map without the mapping for `k`.
	* This method will not remove a mapping for a key with the same label but a different type. */
	def remove[T](k: AttributeKey[T]): AttributeMap

	/** Returns true if this map contains a mapping for `k`.
	* If a key with the same label but a different type is defined in this map, this method will return `false`. */
	def contains[T](k: AttributeKey[T]): Boolean

	/** Adds the mapping `k -> value` to this map, replacing any existing mapping for `k`.
	* Any mappings for keys with the same label but different types are unaffected. */
	def put[T](k: AttributeKey[T], value: T): AttributeMap

	/** All keys with defined mappings.  There may be multiple keys with the same `label`, but different types. */
	def keys: Iterable[AttributeKey[_]]

	/** Adds the mappings in `o` to this map, with mappings in `o` taking precedence over existing mappings.*/
	def ++(o: Iterable[AttributeEntry[_]]): AttributeMap

	/** Combines the mappings in `o` with the mappings in this map, with mappings in `o` taking precedence over existing mappings.*/
	def ++(o: AttributeMap): AttributeMap

	/** All mappings in this map.  The [[AttributeEntry]] type preserves the typesafety of mappings, although the specific types are unknown.*/
	def entries: Iterable[AttributeEntry[_]]

	/** `true` if there are no mappings in this map, `false` if there are. */
	def isEmpty: Boolean
}
object AttributeMap
{
	/** An [[AttributeMap]] without any mappings. */
	val empty: AttributeMap = new BasicAttributeMap(Map.empty)

	/** Constructs an [[AttributeMap]] containing the given `entries`. */
	def apply(entries: Iterable[AttributeEntry[_]]): AttributeMap = empty ++ entries

	/** Constructs an [[AttributeMap]] containing the given `entries`.*/
	def apply(entries: AttributeEntry[_]*): AttributeMap = empty ++ entries

	/** Presents an `AttributeMap` as a natural transformation. */
	implicit def toNatTrans(map: AttributeMap): AttributeKey ~> Id = new (AttributeKey ~> Id) {
		def apply[T](key: AttributeKey[T]): T = map(key)
	}
}
private class BasicAttributeMap(private val backing: Map[AttributeKey[_], Any]) extends AttributeMap
{
	def isEmpty: Boolean = backing.isEmpty
	def apply[T](k: AttributeKey[T]) = backing(k).asInstanceOf[T]
	def get[T](k: AttributeKey[T]) = backing.get(k).asInstanceOf[Option[T]]
	def remove[T](k: AttributeKey[T]): AttributeMap = new BasicAttributeMap( backing - k )
	def contains[T](k: AttributeKey[T]) = backing.contains(k)
	def put[T](k: AttributeKey[T], value: T): AttributeMap = new BasicAttributeMap( backing.updated(k, value) )
	def keys: Iterable[AttributeKey[_]] = backing.keys
	def ++(o: Iterable[AttributeEntry[_]]): AttributeMap =
	{
		val newBacking = (backing /: o) { case (b, AttributeEntry(key, value)) => b.updated(key, value) }
		new BasicAttributeMap(newBacking)
	}
	def ++(o: AttributeMap): AttributeMap =
		o match {
			case bam: BasicAttributeMap => new BasicAttributeMap(backing ++ bam.backing)
			case _ => o ++ this
		}
	def entries: Iterable[AttributeEntry[_]] =
		for( (k: AttributeKey[kt], v) <- backing) yield AttributeEntry(k, v.asInstanceOf[kt])
	override def toString = entries.mkString("(", ", ", ")")
}

// type inference required less generality
/** A map entry where `key` is constrained to only be associated with a fixed value of type `T`. */
final case class AttributeEntry[T](key: AttributeKey[T], value: T)
{
	override def toString = key.label + ": " + value
}

/** Associates a `metadata` map with `data`. */
final case class Attributed[D](data: D)(val metadata: AttributeMap)
{
	/** Retrieves the associated value of `key` from the metadata. */
	def get[T](key: AttributeKey[T]): Option[T] = metadata.get(key)

	/** Defines a mapping `key -> value` in the metadata. */
	def put[T](key: AttributeKey[T], value: T): Attributed[D] = Attributed(data)(metadata.put(key, value))

	/** Transforms the data by applying `f`. */
	def map[T](f: D => T): Attributed[T] = Attributed(f(data))(metadata)
}
object Attributed
{
	/** Extracts the underlying data from the sequence `in`. */
	def data[T](in: Seq[Attributed[T]]): Seq[T] = in.map(_.data)

	/** Associates empty metadata maps with each entry of `in`.*/
	def blankSeq[T](in: Seq[T]): Seq[Attributed[T]] = in map blank

	/** Associates an empty metadata map with `data`. */
	def blank[T](data: T): Attributed[T] = Attributed(data)(AttributeMap.empty)
}